Portable lantern



1.1 is a top, front, and side perspective view of a portable lantern showing my new design;

1.2 is a front elevation view thereof;

1.3 is a rear elevation view thereof;

1.4 is a right side elevation view thereof;

1.5 is a left side elevation view thereof;

1.6 is a top plan view thereof; and

1.7 is a bottom plan view thereof.

The broken lines in the reproductions illustrate portions of the portable lantern that form no part of the claimed design. 

CLAIM The ornamental design for a portable lantern, as shown and described. 